“Brain cleaning” and migraine attacks: what’s the connection?

A major breakthrough came in 2012, when Danish-American neuroscientist Maiken Niedergaard and her team first described the glymphatic system. Working alongside the body’s lymphatic system, it helps clear waste from the brain in an effective and reliable way. (See this article describing the glymphatic system and what it does.) Niedergaard’s discovery sparked a wave of international research, and the glymphatic system has since become a key topic in neuroscience.

What powers brain clearance?

Since then, one of the main questions has been what actually powers this system. Researchers discovered that the answer lies in the brain’s blood vessels. As they pulsate, they create a kind of wave that pushes fluid through the glymphatic system. The spaces around the blood vessels where this fluid flows widen and narrow with each pulse, effectively driving circulation and helping to clear waste.

This immediately raised additional questions: what happens if this process is disturbed, and what might cause this? Research on dementia had already hinted that waste clearance in the brain isn’t always completely effective. The presence of persistent protein deposits, which are known as plaques and linked to dementia, suggests that not everything is successfully removed. Researchers concluded that the brain’s waste clearance system doesn’t always do its job properly.

The glymphatic system and migraine

This led researchers to wonder whether natural limitations in brain clearance might also be relevant in headache disorders and conditions such as migraine. It was known that, during a migraine attack, waves of activity spread across the brain’s cortex (read more here). It was also known that these waves of hyperactivity (known as cortical spreading depression, or CSD) increase the risk of vascular events in the brain, including strokes. Given the major impact on blood vessels, it was logical to wonder if CSD might also interfere with the brain’s clearance processes.

Is the clearance flow disrupted?

A team at Harvard Medical School in Boston set out to find out more about what happens to the blood vessels during the wave of activity in the brain and investigate any links with migraine. Using advanced imaging techniques in laboratory mice, they were able to visualise the fluid-filled spaces around blood vessels and watch how they changed during a wave. What they saw was striking: the spaces narrowed, and fluid movement through them was significantly reduced. Further tissue measurements using sophisticated techniques backed this up.

The results suggest that glymphatic flow is probably impaired while a wave is spreading, meaning the brain’s usual clearance function cannot operate properly. In their animal models, the researchers noted that simulated migraine attacks disrupted normal brain activity, impairing blood flow in the affected parts of the brain and interfering with toxin and waste removal. If these findings translate to humans, it raises the possibility that frequent or prolonged migraine attacks could damage, or at least significantly increase the burden on, the brain due to buildup of metabolic waste.

What about sleep?

Sleep, particularly deep sleep, is when the glymphatic system is at its most active. Brain cleaning works best during deep sleep, meaning that deep sleep is essential for brain health. When sleep is disturbed, various signalling and inflammatory substances can build up. These are known to be involved in triggering migraine attacks.

The problem is that headaches themselves can disrupt your sleep. This can create a vicious cycle, with poor sleep triggering attacks, and attacks further impairing sleep quality. Many studies report that people with migraine often experience worse sleep, with a tendency for attacks to occur in the early morning. This has led researchers to suspect a link between nighttime disruption of glymphatic activity and morning onset of symptoms.

That said, the evidence needs to be treated with caution. Many studies are small and difficult to replicate. A lot more research will be needed to be able to draw firm conclusions about cause and effect. Even so, there does seem to be a close connection between sleep, the glymphatic system and migraine. Overall, emerging research highlighting the importance of this link is growing rapidly.

Sleep and migraine: what do I need to know?

Brain clearance during sleep is hard work for the brain. It takes both time and energy. Our energy stores become exhausted at night and need to be replenished. If you don’t get enough sleep, your brain will not get the time it needs to complete its “cleaning shift”. On the other hand, sleeping too long puts more strain on the brain, without refilling its energy stores in time. Either way, the instability is a typical migraine trigger.

Anyone prone to migraine attacks should aim for a consistent sleep schedule, going to bed and getting up at similar times every day – weekends included. For people with migraine, regularity matters a lot. Good sleep hygiene also helps. That means winding down properly before going to bed. Avoiding screens before bed is a good idea. If switching off is difficult, you may want to try relaxation techniques before bedtime. Jacobson’s progressive muscle relaxation is a highly recommended headache prevention exercise (available in the Prevent Headache app or here). When you wake up the next morning, it helps to eat a proper breakfast soon after getting up. After a hard night’s work, your brain urgently needs new energy to get through the day.